Transfer molding method and transfer molding apparatus

ABSTRACT

A transfer molding method has a transfer molding step of performing transfer molding to a resin sheet between a first die and a second die, which are disposed while facing each other, by heating at least one of the first and second dies, and a cooling step of cooling the resin sheet. The cooling step includes a first cooling step of cooling the resin sheet while an applied pressure is maintained at a first setting value smaller than a value of an applied pressure in the transfer molding step, and a second cooling step of cooling the resin sheet while the applied pressure is reduced to a second setting value smaller than the first setting value.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims priority from Japanese Patent ApplicationNo. 2012-244011, filed on Nov. 5, 2012, the subject matter of which ishereby incorporated by reference.

BACKGROUND

1. Technical Field

The present invention relates to a transfer molding method and atransfer molding apparatus.

2. Related Art

Conventionally, there is well known a transfer molding apparatus thatheats and pressurizes a resin film with a transfer plate to performtransfer molding of a fine irregular pattern (for example, see JapaneseUnexamined Patent Publication No. 2005-310286).

However, in the conventional transfer molding apparatus, the whole dieis heated and cooled. Therefore, an energy loss is increased. A timenecessary for one cycle of the transfer molding is lengthened.Additionally, because the whole die is repeatedly expanded andcontracted, each component is severely degraded.

SUMMARY

One or more embodiments of the present invention suppresses energy loss,performs transfer molding in a short time, and enhances durability ofthe apparatus.

In accordance with one or more embodiments of the present invention, atransfer molding method includes: a transfer molding step of performingtransfer molding to a resin sheet nipped between a first die and asecond die, which are disposed while facing each other, by heating atleast one of the first and second dies; and a cooling step of coolingthe resin sheet, wherein the cooling step includes: a first cooling stepof cooling the resin sheet while an applied pressure is maintained at afirst setting value smaller than a value of an applied pressure in thetransfer molding step; and a second cooling step of cooling the resinsheet while the applied pressure is reduced to a second setting valuesmaller than the first setting value.

Accordingly, the resin sheet is cooled while pressurized in the firstcooling step, whereby the bubble can be melted and eliminated in themolten resin. Then, in the second cooling step, the resin sheet iscooled while the applied pressure is reduced, whereby the residualstress can be released, and the subsequent deformation can be prevented.

In a transfer molding method according to one or more embodiments of thepresent invention, the cooling step further includes a third coolingstep of cooling the resin sheet while the applied pressure is increasedagain to a third setting value higher than the second setting value.

Even if the resin sheet is unevenly cooled, the applied pressure isincreased again in the third cooling step, so that the resin sheet canbe formed into the desired shape.

In a transfer molding method according to one or more embodiments of thepresent invention, a heating temperature of one of the first and seconddies is higher than a heating temperature of the other die in thetransfer molding step, and a surface of the resin sheet, which islocated on a side on which the die is heated to the higher temperature,is cooled in the cooling step.

Accordingly, a resin sheet conveying line can be disposed near the diehaving the lower temperature. Therefore, in opening the dies, an openingamount is suppressed to implement a compact configuration. The both thesurfaces of the resin sheet, the surface, which is located on the sideon which the die is heated to the higher temperature, is intensitivelycooled, so that the resin sheet can quickly be solidified.

In a transfer molding method according to one or more embodiments of thepresent invention, the applied pressure is increased again at least onetime when the temperature on a cooling side of the resin sheet islowered to a glass transition temperature or less.

Accordingly, when the temperature at the resin sheet is lowered to theglass transition temperature or less to solidify the resin sheet, thegeneration of the warp can effectively be suppressed by increasing theapplied pressure again.

The applied pressure may be increased again in the third cooling step.

In a transfer molding method according to one or more embodiments of thepresent invention, a warp amount of a post-transfer-molding product isadjusted by changing a time of the third cooling step.

Accordingly, post-machining process and the like are eliminated, and thedesired warp amount can be set according to use application.

In accordance with one or more embodiments of the present invention, atransfer molding apparatus includes: a first die; a second die that canrelatively be separated from and come into contact with the first die; aheater that is provided in at least one of the first and second dies; atransfer member that is provided in at least one of the first and seconddies while being able to be separately moved from the die, the transfermember performing transfer molding while abutting a transfer surface ona resin sheet supplied between the first and second dies; a coolingmember that abuts on and cools a surface on an opposite side of asurface, in which the transfer surface of the transfer member is formed,while separately moving the transfer member from the die; and acontroller that brings the first and second dies close to each other,nips the cooling member, the transfer member, and the resin film, coolsthe resin sheet while an applied pressure is maintained at a firstsetting value smaller than an applied pressure in the transfer molding,and further cools the resin sheet while the applied pressure is reducedto a second setting value smaller than the first setting value.

In a transfer molding apparatus according to one or more embodiments ofthe present invention, the controller further cools the resin sheetwhile the applied pressure is reduced to a second setting value smallerthan the first setting value.

In a transfer molding apparatus according to one or more embodiments ofthe present invention, the transfer member can relatively separately bemoved from the die.

According to one or more embodiments of the present invention, thetransfer molding apparatus further includes a cooling part that coolsthe transfer member relatively separately moved from the die.

According to one or more embodiments of the present invention, thecooling step is divided into the first cooling step and the secondcooling step, and the bubble can be melted and eliminated in the moltenresin by the pressurization in the first cooling step. In the secondcooling step, the residual stress can be removed by reducing thepressure. Accordingly, the resin sheet can be formed into the desiredshape with no deformation after the transfer molding.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic front view illustrating a light guide plateforming apparatus according to a first embodiment;

FIG. 2 is a partially exploded perspective view schematicallyillustrating a transfer molding apparatus in FIG. 1;

FIG. 3A is a partial plan view of an upper-die transfer plate in FIG. 2,FIG. 3B is a partially schematic sectional view of a die portion in FIG.2, and FIG. 3C is a partially enlarged view of the die portion in FIG.2;

FIG. 4A is am explanatory view illustrating a relationship between ahalf-finished plate and first and second cutting tools, and FIGS. 4B and4C are explanatory views illustrating a relationship between thehalf-finished plate and the first cutting tool;

FIG. 5A is a photograph illustrating a lighting state of a light guideplate of the first embodiment, FIG. 5B is a photograph illustrating alighting state of a conventional light guide plate, and FIG. 5C is agraph illustrating transmitted light amounts of the lighting states inFIGS. 5A and 5B;

FIG. 6 is a schematic perspective view illustrating a light guide plateforming apparatus according to a second embodiment;

FIG. 7A is an explanatory view illustrating a behavior of each plate ina transfer molding apparatus in FIG. 6;

A part (a) of FIG. 7B is a graph illustrating a change in elasticmodulus of a resin sheet according to a temperature change of the resinsheet, and a part (b) of FIG. 7B is a graph illustrating a change inresidual stress according to the temperature change of the resin sheet;

FIG. 8 is a graph illustrating a relationship between a temperature andan applied pressure in a die of the transfer molding apparatus in FIG.6;

FIG. 9 is an explanatory view illustrating a behavior of each plate in atransfer molding apparatus according to a third embodiment;

FIG. 10 is an explanatory view illustrating the behavior of each platein the transfer molding apparatus of the third embodiment;

FIG. 11A is a schematic explanatory view illustrating a method accordingto other embodiments for forming a thick portion from the resin sheet;

FIG. 11B is a schematic explanatory view illustrating a method accordingto other embodiments for forming the thick portion from the resin sheet;

FIG. 11C is a schematic explanatory view illustrating a method accordingto other embodiments for forming the thick portion from the resin sheet;

FIG. 11D is a partially schematic sectional view illustrating a transferplate and the resin sheet according to other embodiments;

FIG. 11E is a sectional view illustrating a liquid crystal displaydevice in which the light guide plate of the first embodiment is used;and

FIG. 11F is a perspective view illustrating an area light source devicein which the light guide plate of other embodiments is used.

DETAILED DESCRIPTION

Hereinafter, embodiments of the present invention will be described withreference to the accompanying drawings. In the following description,terms indicating a specific direction or position (for example, a termincluding “upper”, “lower”, “side”, and “end”) are used. The terms areused in the drawings only for the purpose of easy understanding of thepresent invention, but the technical scope of the present invention isnot limited to the term. The following description is made only by wayof example, but the present invention and application of the presentinvention are not limited to the following description. In embodimentsof the invention, numerous specific details are set forth in order toprovide a more thorough understanding of the invention. However, it willbe apparent to one of ordinary skill in the art that the invention maybe practiced without these specific details. In other instances,well-known features have not been described in detail to avoid obscuringthe invention.

(First Embodiment)

(Configuration)

FIG. 1 illustrates a light guide plate forming apparatus according to afirst embodiment. The light guide plate forming apparatus includes amaterial supply apparatus 1, a transfer molding apparatus 2, a filmadhesion apparatus 3, a cutting apparatus 4, and an outer shapemachining apparatus 5.

The material supply apparatus 1 rewinds a resin sheet 25 wound around amain roller 6, and supplies the resin sheet 25 to the transfer moldingapparatus 2. Plural rollers 7 are disposed in the material supplyapparatus 1, a protective sheet adhering to the resin sheet 25 is peeledoff immediately after the second roller 7, and the protective sheet iswound by a winding roller 8. At this point, the resin sheet 25 is madeof polycarbonate (a melting point of about 240° C. and aglass-transition temperature of about 150° C.).

As illustrated in FIG. 2, the transfer molding apparatus 2 includes alower die 9 and an upper die 10.

In the lower die 9, a lower-die intermediate plate 12, a lower-dieheat-insulating plate 13, and a lower-die transfer plate 14 are disposedin this order on an upper surface of a lower-die support plate 11.

The lower-die support plate 11 made of stainless steel (SUS) is formedinto a rectangular plate shape when viewed from above. Pluralthrough-holes are made between side surfaces of the lower-die supportplate 11, and heaters 15 and thermocouples (not illustrated) areinserted in the through-holes. The lower-die support plate 11 is heatedby energizing the heaters 15, and a temperature at the lower-dietransfer plate 14 can be raised through the lower-die intermediate plate12 and the lower-die heat-insulating plate 13. At this point, thetemperature at the lower-die support plate 11, which is heated byenergizing the heaters 15, is suppressed to about 180° C.

Like the lower-die support plate 11, the lower-die intermediate plate 12made of stainless steel (SUS) is formed into the rectangular plate shapewhen viewed from above.

The lower-die heat-insulating plate 13 is constructed by stacking pluralheat-insulating sheets 13 a made of resin materials, such as polyimide(in FIG. 2, the lower-die heat-insulating plate 13 is illustrated whilevertically taken apart). Heat-insulating performance can be adjustedaccording to the number of stacked heat-insulating sheets 13 a. At thispoint, the lower-die heat-insulating plate 13 is constructed by the fiveheat-insulating sheets, whereby the lower-die transfer plate 14 isadjusted at the temperature of about 150° C. while the lower-die supportplate 11 is heated to the temperature of about 180° C. This prevents adeformation of the resin sheet 25, which is caused by a thermalinfluence of the lower-die support plate 11. Accordingly, a conveyingline for the resin sheet 25 is disposed near the lower die 9, but it isnot necessary to increase a distance in opening the dies, which allowsdownsizing of the transfer molding apparatus 2. In closing the dies toheat the resin sheet 25, the lower-die heat-insulating plate 13 plays arole in preventing a heat loss from the upper die 10 onto the lower dieside. In cooling the resin sheet 25, the lower-die heat-insulating plate13 plays a role in preventing the lower-die support plate 11 from beingcooled.

The lower-die transfer plate 14 made of a nickel chrome alloy is formedinto the rectangular plate shape when viewed from above. A transfersurface is formed on an upper surface of the lower-die transfer plate14. In the transfer surface, plural hemispherical recesses havingsub-micrometer-scale depths are disposed at arbitrary intervals in anx-axis direction and a y-axis direction. Therefore, the pluralhemispherical protrusions can be formed on a lower surface of the resinsheet 25 that is of a transfer destination. A surface in which theprotrusions are formed constitutes a reflecting surface. The surfacefunctions to reflect light emitted from a light source onto the uppersurface side and to output the light through the upper surface. Therecess is not limited to the hemispherical shape, but various recessedshapes, such as a conical shape, may be used as the recess. Not therecess, but a projection may be formed.

A horizontal surface of the lower die 9 can be moved in the x-axisdirection and the y-axis direction by driving parts (not illustrated),such as a servo motor. A movement amount of the lower die 9 is detectedby a micrometer 16, and a position in the horizontal surface of thelower die 9 can finely be adjusted in the x-axis direction and they-axis direction based on the detection result. The lower die 9 maymanually be moved.

In the upper die 10, an upper-die intermediate plate 18, an upper-dieheat-insulating plate 19, and a retention plate 21 that retains anupper-die transfer plate 20 are disposed in this order on a lowersurface of an upper-die support plate 17.

Like the lower-die support plate 11, the upper-die support plate 17 madeof stainless steel (SUS) is formed into the rectangular plate shape whenviewed from above. Plural through-holes are made between the sidesurfaces of the upper-die support plate 17, and heaters 22 andthermocouples (not illustrated) are inserted in the through-holes. Theupper-die support plate 17 can be raised up to the temperature of about280° C. by energizing the heaters 22.

Like the upper-die support plate 17, the upper-die intermediate plate 18made of stainless steel (SUS) is formed into the rectangular plate shapewhen viewed from above.

Like the lower-die heat-insulating plate 13, the upper-dieheat-insulating plate 19 is constructed by stacking pluralheat-insulating sheets 19 a made of resin materials, such as polyimide.At this point, the upper-die heat-insulating plate 19 is constructed bythe two heat-insulating sheets, whereby the upper-die transfer plate 20is adjusted to the temperature of about 240° C. Therefore, the resinsheet 25 can sufficiently be melted when the resin sheet 25 issandwiched between the upper die 10 and the lower die 9.

Like the lower-die transfer plate 14, the upper-die transfer plate 20made of a nickel chrome alloy is formed into the rectangular plate shapewhen viewed from above. As illustrated in FIG. 3, a recess 23 extendedin a width direction is formed in the lower surface of the upper-dietransfer plate 20. As illustrated in FIG. 3C, the recess 23 is a spacesurrounded by a perpendicular surface 23 a, a bottom surface 23 b, aninclined surface 23 c, and both end faces (not illustrated). Plural arcregions 24 are arrayed in the width direction in the inclined surface 23c. In each arc region 24, plural projected thread portions (notillustrated), each of which is radially extended and has a substantiallytriangular shape in section, are arrayed in a circumferential direction.

The recess 23 is configured such that the molten resin sheet 25 flowspartially into the recess 23 to form a thick portion 26. The resin sheet25 includes an extremely thin film, films having thicknesses of 0.2 to0.3 mm used in the first embodiment, and films having thickness greaterthan the thicknesses of 0.2 to 0.3 mm. The thick portion 26 has asub-millimeter-scale height. In the first embodiment, the thick portion26 has the height of 0.2 mm. The projected thread portion formed in theinclined surface has a sub-micrometer-scale projection (surfaceroughness). In the first embodiment, the projected thread portion hasthe projection of 0.2 μm. A region where the projected thread portionsare formed is the transfer surface, and the region suppresses the lightleaking from the inclined surface 23 c by folding the light incidentfrom the plural light sources disposed on the end face side of the thickportion 26.

Plural groove portions 27 that provide communication between the recess23 and the side surface are formed in the lower surface of the upper-dietransfer plate 20. According to one or more embodiments of the presentinvention, each groove portion 27 is formed in the direction (the x-axisdirection) orthogonal to the width direction (the y-axis direction) inwhich the recess 23 is extended. Therefore, the groove portion 27 can beshortened to the minimum. Each groove portion 27 is also formed so as tobe located between the arc regions 24 and 24. This is because a flowrate of the molten resin becomes the slowest in the region between thearc regions 24 to easily leave a bubble. Therefore, the bubble caneffectively be exhausted from the recess 23. The groove portion 27 mayhave a depth greater than or equal to that of the recess 23. In thefirst embodiment, the depth of each groove portion 27 is identical tothat of the recess 23. The width of the groove portion 27 is set to avalue such that the bubble does not remain in the recess 23 while anoutflow amount of molten-state resin (resin sheet 25) flowing into therecess 23 is suppressed to the minimum.

Thus, the groove portion 27 that provides communication between therecess 23 and the outside is formed between the arc regions 24 and 24,which allows the air in the recess 23 to be smoothly guided to theoutside when the molten resin flows into the recess 23. Part of theresin flowing into the recess 23 also flows to the groove portion 27.Because the groove portion 27 has the depth greater than or equal tothat of the recess 23, the air does not remain in the region from therecess 23 to the groove portion 27 (when the groove portion 27 is lessthan the recess 23 in the depth, a corner portion is formed, and the airpossibly remains in the corner portion). Accordingly, the air does notremain in the recess 23 and a void is not generated in the thick portion26. A burn is not generated in the resin, because an insignificantamount of air remains in the recess 23 even if the air remains.Additionally, the air can be melted in the molten resin by an appliedpressure force without generating the void.

As illustrated in FIG. 2, the retention plate 21 made of stainless steel(SUS) is formed into the rectangular frame shape, and an opening 28 isformed in the center of the retention plate 21. The upper-die transferplate 20 is retained in the lower surface of the retention plate 21, andexposed upward from the opening 28. The upper surface of the upper-dietransfer plate 20, which is exposed from the opening 28, is irradiatedwith a soft X-ray using a soft X-ray irradiation apparatus 29.Therefore, electricity of the resin sheet 25 is removed, and surroundingdust is prevented from adhering to the resin sheet 25 due to anelectrostatic attraction force. Rods 30 are coupled to both sideportions of the retention plate 21, and the retention plate 21 can belifted and lowered independently of the whole upper die 10 using drivingparts (not illustrated), such as a cylinder.

The whole upper die 10 is lifted and lowered by a press machine 31disposed on the upper surface side of the upper-die support plate 17. Anair supply apparatus 32 supplies and exhausts the air to and from thepress machine 31, and the rods 30 (not illustrated) are lifted andlowered to lift and lower the whole upper die 10 with the upper-diesupport plate 17 interposed therebetween.

The resin sheet 25 supplied by the material supply apparatus 1 isconveyed between the upper die 10 and the lower die 9. On an entranceside and an exit side of the die in the middle of the conveying route ofthe resin sheet 25, a support roller 33 that supports the lower surfaceof the resin sheet 25 and a positioning gripper 34 that vertically nipsthe resin sheet 25 are disposed in the order located closer to the diewhile being able to be lifted and lowered. A conveying gripper 35 isdisposed on a downstream side of the conveying route. Like thepositioning gripper 34, the conveying gripper 35 vertically nips theresin sheet 25, and reciprocally moves along the conveying route by adriving part (not illustrated). In the state in which the positioninggripper 34 is opened, the conveying gripper 35 moves onto the downstreamside of the conveying route while nipping the resin sheet 25, whichallows the resin sheet 25 to be conveyed. Behaviors of the supportroller 33 and the grippers are described later.

An air supply duct 36 is disposed on the upper side on the upstream sideof the die, and an exhaust air duct 37 is disposed on the upper side onthe downstream side of the die. The air supplied by a compressor (notillustrated) blows from the air supply duct 36, and the air blows on theresin sheet 25 located between the upper die 10 and the lower die 9 fromobliquely above. The air is sucked from the exhaust air duct 37 by thecompressor (not illustrated), and the air blowing on the resin sheet 25is collected from the air supply duct 36. The air supplied from the airsupply duct 36 is purified, an air flow formed from the air supply duct36 to the exhaust air duct 37 not only cools the resin sheet 25, butalso forms what is called an air barrier to prevent the dust fromadhering to the surface of the resin sheet 25. Because the electricityof the resin sheet 25 is removed by the irradiation of the soft X-ray,the dust does not adhere to the resin sheet 25 due to the electrostaticattraction force.

As illustrated in FIG. 1, adhesive rollers 38 that come into contactwith the upper and lower surfaces of the resin sheet 25 are disposed onthe upstream side of the die. When the adhesive rollers 38 are rotated,each of the adhesive rollers 38 removes the dust adhering to the surfaceof the resin sheet 25 while conveying the resin sheet 25.

The film adhesion apparatus 3 causes protective films 39 to adhere tothe upper and lower surfaces of the resin sheet 25 after the transfermolding. The protective film 39 prevents the resin sheet 25 from beingdamaged due to a collision with another member, or prevents the dustfrom adhering to the surface of the resin sheet 25.

The cutting apparatus 4 cuts the resin sheet 25, to which the transfermolding is performed, into a reed shape. Four sides of the resin sheet25 cut by the cutting apparatus 4 are cut by a punching apparatus (notillustrated) to constitute a half-finished plate 46. In thehalf-finished plate 46, cutting margins are left in the thick portion 26and the end face on the opposite side of the thick portion 26.

The outer shape machining apparatus 5 includes a cutting member 41 thatcuts both the end faces (the thick portion 26 and the side surface onthe opposite side of the thick portion 26) of the half-finished plate46. As illustrated in FIG. 4A, the cutting member 41 includes a firstcutting tool 48 a and a second cutting tool 48 b. The cutting tools 48 aand 48 b are rotated by driving pads (not illustrated). The firstcutting tool 48 a has a cylindrical shape, and a cutting edge 49 a isprovided at a position, which is point-symmetric in relation to arotating axis, in an outer circumferential surface of the first cuttingtool 48 a, for coarse finishing. The second cutting tool 48 b has a discshape, notches are formed at two symmetric positions in the outercircumference of the second cutting tool 48 b, and radially-extendedcutting edges 49 b are formed in the surface. The second cutting tool 48b is used in mirror finish. A specific cutting method performed by thecutting member 41 is described later.

(Behavior)

A behavior of the light guide plate forming apparatus having the aboveconfiguration will be described below.

(Preparation Process)

The upper die 10 is lifted to open the die, and the leading end portionof the resin sheet 25 supplied from the material supply apparatus 1 isnipped by the conveying gripper 35. After the conveying gripper 35 ismoved, the resin sheet 25 is nipped by the positioning gripper 34 todispose the resin sheet 25 in a region where the upper die 10 and thelower die 9 face each other (conveying process).

The die is previously heated by energizing the heater 15. As describedabove, because the heat-insulating plate is interposed, the upper-dietransfer plate 20 becomes about 240° C. in the upper die 10, and thelower-die transfer plate 14 becomes about 150° C. in the lower die 9. Inthe lower die 9 located near the resin sheet 25, the temperature of theupper surface of the lower die 9 is suppressed to around aglass-transition temperature, and the resin sheet 25 is bent downward bya thermal influence. Therefore, a trouble such that the resin sheet 25comes into contact with the lower-die transfer plate 14 is not generated(preheating process).

(Transfer Molding Process)

The support roller 33 and the positioning gripper 34 are lowered toplace the resin sheet 25 on the lower-die transfer plate 14 of the lowerdie 9. The press machine 31 is driven to lower the upper die 10, and thetransfer surface of the upper-die transfer plate 20 is abutted on theresin sheet 25. At this point, a pressure acting on the press machine 31is suppressed to a low level, and the resin sheet 25 is lightly nippedbetween the dies. Therefore, the resin sheet 25 is heated to remove amoisture included in a surface layer (preheating process).

The pressure applied by the press machine 31 is increased when apreviously-set time (a first setting time) elapses since the preheatingprocess is started. As described above, the resin sheet 25 is made ofpolycarbonate (the melting point of about 250° C. and theglass-transition temperature of about 150° C.). Because the upper-dietransfer plate 20 is heated to 240° C., the temperature of the resinsheet 25 exceeds the melting point, and the resin sheet 25 becomes themolten state. In the lower die 9, although the lower-die transfer plate14 has the temperature of 180° C., the heat is not lost from the lowerdie side because the lower-die heat-insulating plate 13 is disposed.Therefore, the whole region of the resin sheet 25 nipped by the diesexceeds the melting point to become the molten state (heating andpressurization process).

The pressure is applied from the upper die 10 by the press machine 31.Therefore, the resin sheet 25 is thinned in the portion nipped by thedies, and part (an upper surface portion) of the resin sheet 25 flowsinto the recess 23 formed in the upper-die transfer plate 20. When themolten resin flows into the recess 23, the air in the recess 23 isexhausted to the outside through the groove portion 27. The recess 23 iscompletely filled with the molten resin, and part of the molten resinflows out to the groove portion 27. The depth of the groove portion 27is greater than or equal to the depth of the recess 23 (in this case,the same depth). Therefore, the air does not remain in the recess 23,but the air is smoothly exhausted to the outside. Troubles, such as theburn, are not generated because the air is not compressed in the recess23. Even if a small amount of air remains in the recess 23, because thesufficient pressure is applied to the recess 23, the air can be meltedin the molten resin without generating the void.

The upper die 10 is lifted when a previously-set time (a second settingtime) elapses since the heating and pressurization process is started.However, the upper-die transfer plate 20 remains abutted on the resinsheet 25 by driving the cylinder. At this point, the air is suppliedonto the upper-die transfer plate 20 through the air supply duct 36. Theheated upper-die support plate 17 is distant from the resin sheet 25,and the air blows onto the upper-die transfer plate 20 from the airsupply duct 36. That is, the resin sheet 25 can be cooled only throughthe upper-die transfer plate 20. The heat of the upper-die support plate17 does not affect the cooling of the resin sheet 25, so that the resinsheet 25 can effectively be cooled in a short time. That is, the resinsheet 25 can be cooled in a short time to temperatures of 150° C., whichis of the glass-transition temperature of polycarbonate, or less. Inthis case, because the upper-die support plate 17 and the upper-dieintermediate plate 18 are not cooled, an energy loss is decreased, andthe next transfer molding process can smoothly be started in a shorttime (cooling process).

When a previously-set time (a third setting time) elapses since thecooling process is started, namely, when the molten resin is solidifiedto stabilize the shape by the cooling, the upper-die transfer plate 20is lifted and released from the molded portion. The support roller 33 islifted to release the molded portion from the lower-die transfer plate14. Therefore, the thick portion 26 having the sub-millimeter-scaleheight, namely, the height of 0.2 mm is formed on the upper surface ofthe resin sheet 25. The plural projected thread portions having thesub-micrometer-scale saw-tooth shapes, namely, the 14-μm saw-toothshapes are formed on the inclined surface of the thick portion 26. Onthe other hand, in the lower surface of the resin sheet 25, the pluralhemispherical protrusions are formed at constant intervals in the x-axisdirection and the y-axis direction (die releasing process).

Conventionally, although the sub-micrometer-scale protrusions can beformed in the resin sheet 25 by the transfer molding, thesub-millimeter-scale thick portion 26 cannot simultaneously be formed.The use of the transfer molding apparatus 2 having the die structure cansimultaneously form the sub-micrometer-scale protrusions and thesub-millimeter-scale thick portion 26 in the resin sheet 25. Because thewhole resin sheet 25 nipped between the dies is melted in the transfermolding, the internal stress does not remain in the half-finished plate46 obtained by the solidification of the melted resin sheet 25.Accordingly, plural LEDs are disposed on the end face side of the thickportion 26, and the whole upper surface except the thick portion 26 canevenly be irradiated with the light after the light is transmittedthrough the thick portion 26 without deviation.

(Film Adhesion Process)

The resin sheet 25 to which the transfer molding is performed by thetransfer molding apparatus 2 is further conveyed onto the downstreamside, and the film adhesion apparatus 3 causes the protective films 39to adhere to the upper and lower surfaces of the resin sheet 25. Theprotective film 39 prevents the resin sheet 25 from being damaged due tothe collision with another member, or prevents the generation of thetrouble due to the surrounding dust adhering to the half-finished plate46. The half-finished plate 46 becomes the light guide plate through thesubsequent machining. Then the protective film 39 is peeled off from theresin sheet 25 when the liquid crystal panel is assembled.

(Cutting Process)

The resin sheet 25 in which the protective films 39 adhere to the upperand lower surfaces is further conveyed onto the downstream side, and thecutting apparatus 4 cuts the resin sheet 25 in units of half-finishedplates in the conveying direction to form a reed-shaped resin sheet 25.The half-finished plate 46 has the cutting margins for an outer shapemachining process in the thick portion 26 and the end face (the cuttingsurface) on the opposite side of the thick portion 26. At this point, inthe cutting surface of the half-finished plate 46, a tapered surface 46a is formed in a corner portion on a cutting direction side of the firstcutting tool 48 a described later. The tapered surface 46 a has an angleof about 3° with respect to the cutting surface such that the taperedportion is left after the cutting margin is cut.

(Outer Shape Machining Process)

The eight half-finished plates 46 obtained through the cutting processare stacked such that the thick portions 26 are alternately located onthe opposite sides. Dummy plates 47 are disposed on the upper and lowersurfaces of the stacked half-finished plates 46.

One end face of the half-finished plates 46 and dummy plates 47 is cutusing the first cutting tool 48 a and the second cutting tool 48 b.

As illustrated in FIG. 4A, the first cutting tool 48 a is disposed suchthat the rotating axis of the first cutting tool 48 a is parallel to thecutting surface of the half-finished plate 46, and the first cuttingtool 48 a cuts the end face of the half-finished plate 46 using thecutting edges on the outer circumference while rotated clockwise. Inthis case, the half-finished plates 46 are stacked and nipped betweenthe dummy plates 47. Accordingly, the half-finished plates 46 cansmoothly be cut without generating a flutter during the cutting. In thehalf-finished plate 46, the tapered surface 46 a is formed in the cornerportion on the cutting direction side of the first cutting tool 48 a.The tapered surface 46 a is extended beyond the cutting margin of thecutting surface of the half-finished plate 46. Accordingly, the burrcaused by the first cutting tool 48 a is not generated in the cornerportion of the half-finished plate 46.

As illustrated in FIG. 4B, the second cutting tool 48 b is disposed suchthat the rotating axis of the second cutting tool 48 b is perpendicularto the cutting surface of the half-finished plate 46, and the secondcutting tool 48 b performs the mirror finish to the cutting surfaceusing the cutting edges on the surface of the second cutting tool 48 b.The cutting edges cut the cutting surfaces of the stacked half-finishedplates 46 while being rotated. Unless the dummy plates 47 are disposedon the upper and lower surfaces, possibly the burrs are generated atupper and lower edges of the half-finished plates 46 located on bothsides. However, the dummy plates 46 are disposed on the upper and lowersurfaces. Therefore, even if the burr is generated, the burr isgenerated in not the half-finished plate 46 but the dummy plate 47.

The completed light guide plate includes a thin portion having thethickness of 0.2 mm and a thick portion having the thickness of 0.5 mmand a substantial trapezoid section. Many hemispherical recesses (orprotrusions) are formed in the bottom surface of the light guide plate.The light guide plate is assembled in the following manner as onecomponent of the liquid crystal display device together with othercomponents.

As illustrated in FIG. 11E, a light guide plate 61 is placed on an uppersurface of a base 62. A diffuser plate 63, a prism sheet 64, and aliquid crystal panel 65 are sequentially stacked on the upper surface ofthe light guide plate 61. An LED 66 that is of the light source isdisposed in a lateral portion of a perpendicular surface of the thickportion 49 a. Therefore, a liquid crystal display device 60 iscompleted.

In the completed liquid crystal display device 60, the light emittedfrom the LED 66 is guided to a thin portion 61 b while a projectedthread portion of a thick portion 61 a prevents the light from leakingto the outside. The light is evenly diffused by the hemisphericalrecesses in the bottom surface, and the liquid crystal panel 65 isirradiated with the light through the diffuser plate 63 and the prismsheet 64.

The light guide plate may solely be used as the area light source devicewithout providing the liquid crystal panel 65.

A birefringence state of the light guide plate will be described. Asdescribed above, the whole resin sheet 25 nipped between the dies ismelted in performing the transfer molding. Therefore, an internal stressdoes not remain in the obtained product, but the structure becomeshomogeneous state. Accordingly, as illustrated in FIG. 5A, the light canevenly output from the whole upper surface. On the other hand, for theconventional light guide plate, as illustrated in FIG. 5B, unevenness isgenerated when the light is output from the whole upper surface. FIG. 5Cis a graph illustrating a difference in transmitted light amount betweenP-polarization and S-polarization with respect to the light guideplates. As is clear from the graph in FIG. 5C, in the light guide plateof the first embodiment, the difference in transmitted light amount canbe suppressed to a considerably small level compared with theconventional light guide plate.

(Second Embodiment)

In a transfer molding apparatus according to a second embodiment in FIG.6, a direct cooling method in which the upper-die transfer plate 20 iscooled by bringing a cooling plate 50 into direct contact with theupper-die transfer plate 20 is adopted instead of the air cooling methodin which the upper-die transfer plate 20 is cooled by the air blowingfrom the air supply duct 36.

The cooling plate 50 can reciprocally be moved between a transfer regionin the die and a non-transfer region outside the die by a horizontallymoving mechanism (not illustrated). An auxiliary heat-insulating plate51 is integrally provided on the upper surface of the cooling plate 50.While an upper-side transfer plate is retained in the retention plate21, the lower surface of the upper-side transfer plate can be abutted onthe upper surface of the resin sheet 25, and the lower surface of thecooling plate 50 can be abutted on the upper surface of the upper-sidetransfer plate. The water-cooled type cooling plate 50 is configuredsuch that a liquid flows through a pipe (not illustrated) to maintain asurface temperature of the cooling plate 50 at a constant value (forexample, 20° C.). Because configurations of die and the like of thesecond embodiment are similar to those of the first embodiment, thecorresponding component is designated by the identical numeral, and thedescription is omitted.

In the configuration of the transfer molding apparatus including thecooling plate 50, after the resin sheet 25 is heated and pressurized,the cooling is performed as follows. In the transfer molding process,when the state illustrated in a part (a) of FIG. 7A transitions to thecooling process, the upper die 10 is lifted while the upper-die transferplate 20 is abutted on the resin sheet 25 as illustrated in a part (b)of FIG. 7A, and the cooling plate 50 is laterally inserted between theupper-die transfer plate 20 and the upper-die intermediate plate 18 asillustrated in a part (c) of FIG. 7A.

(First Cooling Process)

As illustrated in a part (d) of FIG. 7A, the lower surface of thecooling plate 50 is abutted on the upper surface of the upper-dietransfer plate 20, and the cooling plate 50 and the auxiliaryheat-insulating plate 51 are nipped between the upper-die transfer plate20 and the upper-die intermediate plate 18. As illustrated in FIG. 8, atthis point, the applied pressure is set to a high level (lower than alevel during heating and pressurization) such that the bubble (void) canbe eliminated from the resin sheet 25 (for example, the applied pressureis set to 0.8 MPa or more by a Boyle-Charle's law such that the bubblehaving a diameter of about 0.4 mm can be decreased to a diameter ofabout 0.1 mm).

(Second Cooling Process)

When the temperature at the resin sheet 25 is lowered to the meltingpoint of the resin sheet 25 or less (for example, 200° C.) (at thispoint, the temperature is managed by a time, at a time point a firstsetting time elapses since the first cooling process is started), theapplied pressure is instantly reduced (for example, the applied pressureis set to 0.1 MPa). As illustrated in a part (a) of FIG. 7B, an elasticmodulus of the resin sheet 25 is increased with decreasing temperature,an elastic deformation of the resin sheet 25 is hardly performed, andthe resin sheet 25 is solidified at the glass transition temperature ofabout 150° C. to lose fluidity. Therefore, as illustrated in a part (b)of FIG. 7B, in the state in which the pressure is still applied to theresin sheet 25 by the die, a residual stress is generated in the resinsheet 25 when the temperature is lowered to about 150° C. Actually theresin sheet 25 becomes a rubber-like elastic body from about 200° C. andthe residual stress is generated. Therefore, in the second embodiment,the residual stress is removed by reducing the applied pressure when thetemperature at the resin sheet 25 is lowered to about 200° C.

(Third Cooling Process)

When the temperature at the resin sheet 25 is lowered to the glasstransition temperature or less (for example, 150° C.) (at this point,the temperature is managed by a time, at a time point a second settingtime elapses since the second cooling process is started), the appliedpressure is increased again (for example, the applied pressure is set to0.5 MPa or more). Because the resin sheet 25 is cooled from the uppersurface side, a temperature distribution of the resin sheet 25 variesinevitably. At a time point the upper surface side of the resin sheet 25is lowered to the glass transition temperature or less and solidified,sometimes the lower surface side of the resin sheet 25 is not lowered tothe glass transition temperature. In this case, the solidified uppersurface side of the resin sheet 25 does not follow thermal shrinkage onthe lower surface side of the resin sheet 25, a central portion of thelower surface rises to generate a warp. However, a shrinkage stress canforcedly be canceled by increasing the applied pressure again.

When the cooling method of the second embodiment is adopted, a coolingtime can be shortened compared with the air cooling of the firstembodiment. Specifically, compared with the cooling time for 110 secondsin the air cooling of the first embodiment, the cooling time can beshortened to 55 seconds in the direct cooling of the second embodiment.Not only the heat-insulating plate is disposed in each of the upper die10 and the lower die 9, but also the auxiliary heat-insulating plate 51is integrally provided on the upper surface of the cooling plate 50.Therefore, even if the cooling plate 50 is maintained at lowtemperature, an influence of the cooling plate 50 on the upper die 10can be suppressed to shorten a recovery time to the next heating andpressurization.

When the resin sheet 25 is cooled as described above, the upper die 10is lifted to horizontally move and retreat the cooling plate 50 asillustrated in a part (e) of FIG. 7A. As illustrated in a part (f) ofFIG. 7A(f), the upper-die transfer plate 20 is lifted to end one cycle.

(Third Embodiment)

As illustrated in FIGS. 9 and 10, a transfer molding apparatus accordingto a third embodiment includes a cooling mechanism in which the resinsheet 25 is vertically cooled from not only the upper surface side ofthe upper-die transfer plate 20 but also the lower surface of thelower-die transfer plate 14.

The transfer molding apparatus of the second embodiment includes thecooling plate 50 in which the auxiliary heat-insulating plate 51 isintegrated on the upper surface. On the other hand, the transfer moldingapparatus of the third embodiment includes a second cooling plate 54 inwhich an auxiliary heat-insulating plate 55 is integrated on the lowersurface in addition to a first cooling plate 52 corresponding to theauxiliary heat-insulating plate 51 in which an auxiliary heat-insulatingplate 53 is integrated on the upper surface. The whole lower die exceptthe lower-die transfer plate 14 can horizontally be moved to a retreatposition. The resin sheet 25, in which the upper-die transfer plate 20is abutted on the upper surface and the lower-die transfer plate 14 isabutted on the lower surface, can be inserted between the first coolingplate 52 and the second cooling plate 54 while the first cooling plate52 and the second cooling plate 54 vertically face each other.

Action of the transfer molding apparatus 2 including the coolingmechanism having the above configuration will be described below.

Like the first and second embodiments, when the preheating process andthe transfer molding process are ended as illustrated in FIG. 9A, theupper die 10 is lifted while the upper-die transfer plate 20 is abuttedon the upper surface of the resin sheet 25 as illustrated in FIG. 9B. Asillustrated in FIG. 9C, while the lower-die transfer plate 14 is abuttedon the lower surface of the resin sheet 25, other portions of the lowerdie 9 are horizontally moved to the retreat position. The upper-dietransfer plate 20 and the lower-die transfer plate 14, which arevertically disposed while facing each other, are horizontally moved, andthe resin sheet 25 in which the upper-die transfer plate 20 and thelower-die transfer plate 14 are abutted on the upper and lower surfacesis disposed between the first cooling plate 52 and the second coolingplate 54. At this point, as illustrated in FIG. 9D, the upper die 10 islowered, and the resin sheet 25 in which the upper-die transfer plate 20and the lower-die transfer plate 14 are abutted on the upper and lowersurfaces is nipped between the first cooling plate and the secondcooling plate. The cooling process of the resin sheet 25 is started byapplying the pressure.

In the cooling process, the resin sheet 25 can evenly cooled in thevertical direction. Accordingly, unlike the second embodiment, it is notnecessary to deal with troubles, such as the warp, through the first tothird cooling processes. That is, the half-finished plate 46 can becompleted with no warp through the single cooling process.

When the cooling process is ended, the first cooling plate 52, thesecond cooling plate 54, and portions except the lower-die transferplate 14 of the lower die 9 are horizontally moved to the originalposition as illustrated in FIG. 10A. When the resin sheet 25 in whichthe upper-die transfer plate 20 and the lower-die transfer plate 14 areabutted on the upper and lower surfaces is located on the lower die 9 asillustrated in FIG. 10B, the upper-die transfer plate 20 is lifted toend one cycle as illustrated in FIG. 10C.

(Additional Embodiments)

The present invention is not limited to the above embodiments, butvarious changes can be made.

For example, in one or more of the above embodiments, the resin sheet 25is melted and part of the molten resin is caused to flow into the recess23 formed in the upper-die transfer plate 20, thereby forming the thickportion 26. Alternatively, the thick portion 26 may be formed asfollows.

In a part (a) of FIG. 11A, the molten resin of a nonproductive portion(except a region constituting the light guide plate) in the resin sheet25 can be mainly caused to flow into the recess 23. That is, a height ofa sidewall 20 a on the nonproductive portion side constituting therecess 23 formed in the upper-die transfer plate 20 is greater than thatof other portions. An inner surface 20 b formed by the sidewall 20 a isconstructed by an inclined surface 20 b so as to be gradually openedfrom the bottom surface side of the recess 23.

Therefore, when the die is brought into contact with the resin sheet 25to apply the pressure in the transfer molding as illustrated in a part(b) of FIG. 11A, the molten resin of the nonproductive portion flowsinto the recess 23 through the inclined surface 20 b of the sidewall 20a as illustrated in a part (c) of FIG. 11A. Then part of the resin onthe product portion side flows also into the recess 23 through aninclined surface 20 c of a sidewall on the other side. In this case, thesidewall 20 a is largely projected, so that an inflow amount of moltenresin can sufficiently be increased in the nonproductive portion.Accordingly, a disposed resin amount can be suppressed to achieve costreduction. As illustrated in a part (d) of FIG. 11A, the recess 23 isfilled with the molten resin. Because the subsequent cooling process issimilar to that of one or more of the above embodiments, the descriptionis omitted.

In a part (a) of FIG. 11B, the resin sheet 25 is not melted and part ofthe molten resin is not caused to flow into the recess 23, but anadditional member (for example, a resin piece 25 a) is supplied to theupper-die transfer plate 20 according to the recess 23. Therefore, asillustrated in a part (b) of FIG. 11B, the thick portion 26 can easilybe formed.

In a part (a) of FIG. 11C, a projection 25 b is previously formed inpart of the resin sheet 25, whereby the additional member is previouslyintegrated. According to one or more embodiments of the presentinvention, the thickness of the projection 25 b is less than thethickness of the thick portion 26, and is greater than the thickness ofthe pre-transfer-molding resin sheet 25. In the configuration in whichthe projection 25 b is provided, a mechanism that supplies theadditional member is eliminated to improve workability.

In one or more of the above embodiments, the recess 23 is formed in theupper-die transfer plate 20. Alternatively, the recess may be providedin the lower-die transfer plate 14, or both the upper-die transfer plate20 and the lower-die transfer plate 14.

The die structure including the upper die 10 and the lower die 9 is usedin one or more of the above embodiments. Alternatively, a die that ishorizontally opened and closed may be used.

In one or more of the above embodiments, the transfer surfaces areformed in the upper-die transfer plate 20 and the lower-die transferplate 14. Alternatively, the transfer surface may be formed in one ofthe upper-die transfer plate 20 and the lower-die transfer plate 14. Thetransfer plates are eliminated, and the transfer surfaces may directlybe formed in the dies (for example, an intermediate plate).

In one or more of the above embodiments, the whole upper-die transferplate 20 is evenly heated. However, the whole upper-die transfer plate20 is not necessarily evenly heated. For example, the neighborhood ofthe recess 23 may intensitively be heated. Therefore, the good moltenstate of the resin can be obtained in the recess 23 to form the goodthick portion 26 in which a shrinkage is not generated.

In one or more of the above embodiments, the resin sheet 25 is heatedand pressurized while nipped between the upper-die transfer plate 20 andthe lower-die transfer plate 14, and the whole resin sheet 25 is melted.Therefore, in at least one of the transfer plates 20 and 14, accordingto one or more embodiments of the present invention, a flow regulatingstructure that regulates the flow of the molten resin is provided in arim portion.

In FIG. 11D, a flow regulating structure is formed in a rim portion ofthe upper surface of the lower-die transfer plate 14. However, it is notnecessary to form the flow regulating structure to surround all the foursides. As long as the molten resin does not flow to the surroundings,the flow regulating structure may discontinuously be provided, or theflow regulating structure may be provided only in both side portions.

In a part (a) of FIG. 11D, the flow regulating structure is constructedby a projected thread portion 14 a that is projected from the uppersurface of the lower-die transfer plate 14. In a part (b) of FIG. 11D,the flow regulating structure is constructed by a groove portion 14 bthat is formed in the upper surface of the lower-die transfer plate 14.In a part (c) of FIG. 11D, the flow regulating structure is constructedby many micro projected portions 14 c that are projected from the uppersurface of the lower-die transfer plate 14. In a part (d) of FIG. 11D,the flow regulating structure is constructed by many micro recessedportions 14 c that are formed in the upper surface of the lower-dietransfer plate 14. The configurations in the parts (a) to (d) of FIG.11D may be formed in the upper-die transfer plate 20, or both thetransfer plates 14 and 20. The flow regulating structure is not limitedto the configurations in the parts (a) to (d) of FIG. 11D, but flowregulating structure having any configuration may be used as long as aflow resistance against the molten resin is increased.

In one or more of the above embodiments, the applied pressure in thecooling process is determined as illustrated in FIG. 8. Alternatively,the applied pressure may be determined as follows.

For example, in the first cooling process, an applied pressure P₁ isdetermined by a Boyle-Charle's law (PV/T=constant) in order to compressthe bubble having the diameter of 0.4 mm to the diameter of 0.1 mm.P ₀ ×V ₀ /T ₀ =P ₁ ×V ₁ /T ₁  (1)

The following values are substituted for the equation (1).

P₀=101325 Pa (atmospheric pressure)

V₀=3.35×10⁻¹¹ m³ (volume of bubble having diameter of 0.4 mm)

T₀=240° C.=513K

V₁=5.23×10⁻¹³ m³ (volume of bubble having diameter of 0.1 mm)

T₁=190° C.=463K

Therefore, P₁=5.85 MPa is obtained.

Accordingly, the bubble having the diameter of 0.4 mm can be compressedto the diameter of 0.1 mm or less by applying pressures of 5.85 MPa ormore.

In the second cooling process, because the temperature at the resinsheet 25 (polycarbonate) is lowered to 190° C., the applied pressure isdecreased to 0.02 MPa (the applied pressure may be decreased to 0 MPa).Therefore, the residual stress is removed.

In the third cooling process, the pressure, which corresponds to theshrinkage stress when the resin sheet 25 (polycarbonate) is lowered fromthe glass transition temperature of 150° C. to the temperature of 130°C. at which the die can be released, is determined as the appliedpressure P₂.That is, P ₂ =E×α

E (elastic modulus)=2.45 GPa

α (linear expansion coefficient of polycarbonate)=7×10⁻⁵

Accordingly, P₂=3.4 MPa is obtained. The deformation caused by theshrinkage stress of the resin sheet 25 during the cooling can beprevented when pressures of P₂=3.4 MPa or more (for example, 6.2 MPa)are applied.

In one or more of the above embodiments, the preparation process, thetransfer molding process, the film adhesion process, and the cuttingprocess are continuously performed by the sequence of parallellyarranged apparatuses. Alternatively, the preparation process, thetransfer molding process, the film adhesion process, and the cuttingprocess may separately be performed, or partially continuously beperformed. In fact, the preparation process, the transfer moldingprocess, the film adhesion process, and the cutting process maysequentially be performed irrespective of the continuity ordiscontinuity. The processes in the transfer molding process mayseparately be performed, or partially continuously be performed.

In one or more of the above embodiments, the maximum height of theirregularity formed in the transfer surface is set to the sub-micrometerscale and the projection of the thick portion 26 is set to thesub-millimeter scale. Alternatively, for example, the maximum height ofthe irregularity is set to a micrometer scale (for example, 200 μm) andthe projection of the thick portion 26 is set to a millimeter scale (forexample, 1 mm). In fact, it is only necessary that the projection of thethick portion 26 be greater than the maximum height of the irregularity.According to one or more embodiments of the present invention, theprojection of the thick portion 26 is greater than or equal to ten timesthe maximum height of the irregularity. When the projection of the thickportion 26 is greater than or equal to ten times the maximum height ofthe irregularity, the projection of the thick portion 26 may be set tothe sub-micrometer scale.

The continuous, belt-like resin sheet 25 is used in one or more of theabove embodiments. Alternatively, the transfer molding may be performedto one (or at least two) half-finished plate 46 as a discontinuous,reed-shaped configuration. In this case, the reed-shaped resin sheet 25may be conveyed by vertically disposing rotatable rollers.

In one or more of the above embodiments, the light guide plate isproduced by the transfer molding method. Alternatively, various opticalmembers, such as the prism sheet, may be produced.

In one or more of the above embodiments, the light guide plate is usedin the liquid crystal display device having the configuration in FIG.11E. Alternatively, for example, the configuration of the light guideplate may be changed and used in an area light source device in FIG.11F.

A light guide plate 70 in FIG. 11F includes a light guide plate body 71having the substantially even thickness and a wedge-shaped lightintroduction part 72. A deflection pattern or a diffusion pattern isformed on a rear surface of the light guide plate body 71, and alenticular lens 73 having a semicircular shape in section is formed onthe surface of the light guide plate body 71. In the light introductionpart 72, an inclined surface 74 is formed from the light introductionpart 72 toward the light guide plate body 71. The thickness of the endface (the light incident surface) of the light introduction part 72 isgreater than the height of the light source 75.

In the area light source device in which the light guide plate 70 havingthe above configuration is used, the thickness of the end face of thelight introduction part 72 can be set greater than the height of thelight source 75. Accordingly, the light emitted from the light source 75can efficiently be taken in the light introduction part 72. The lighttaken in the light introduction part 72 is introduced to the light guideplate body 71, spread in a planar manner, reflected by the deflectionpattern or the diffusion pattern, and output to the outside through thelight exit surface of the light guide plate body 71. At this point, adirectional pattern of the light output through the light exit surfaceis widened by the lenticular lens 73.

Thus, in the area light source device having the above configuration, abalance between the improvement of the light use efficiency of the lightsource 75 and the low profile of the area light source device can beestablished.

In the light guide plate 70, the lenticular lens 73 having thesemicircular shape in section is formed on the surface of the lightguide plate body 71. Alternatively, the surface of the light guide platebody 71 may have other sectional shapes, such as a prism lens having atriangular shape in section.

While the invention has been described with respect to a limited numberof embodiments, those skilled in the art, having benefit of thisdisclosure, will appreciate that other embodiments can be devised whichdo not depart from the scope of the invention as disclosed herein.Accordingly, the scope of the invention should be limited only by theattached claims.

What is claimed is:
 1. A transfer molding apparatus comprising: a firstdie; a second die configured to be separated from and come into contactwith the first die; a heater that is provided in at least one of thefirst and second dies; a transfer member disposed in at least one of thefirst and second dies while being able to be separately moved from thedie, wherein the transfer member performs transfer molding whileabutting a transfer surface on a resin sheet supplied between the firstand second dies; a cooling member that abuts on and cools a surface onan opposite side of a surface, in which the transfer surface of thetransfer member is formed, while separately moving the transfer memberfrom the die; and a controller that brings the first and second diesclose to each other, nips the cooling member, the transfer member, andthe resin film, cools the resin sheet while an applied pressure ismaintained at a first setting value smaller than an applied pressure inthe transfer molding, and further cools the resin sheet while theapplied pressure is reduced to a second setting value smaller than thefirst setting value.
 2. The transfer molding apparatus according toclaim 1, wherein the transfer member can relatively separately be movedfrom the die.
 3. The transfer molding apparatus according to claim 2,further comprising a cooling part that cools the transfer memberrelatively separately moved from the die.
 4. The transfer moldingapparatus according to claim 1, wherein the transfer member canrelatively separately be moved from the die.
 5. The transfer moldingapparatus according to claim 4, further comprising a cooling part thatcools the transfer member relatively separately moved from the die.